linux/fs/cachefiles/daemon.c
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   1/* Daemon interface
   2 *
   3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public Licence
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the Licence, or (at your option) any later version.
  10 */
  11
  12#include <linux/module.h>
  13#include <linux/init.h>
  14#include <linux/sched.h>
  15#include <linux/completion.h>
  16#include <linux/slab.h>
  17#include <linux/fs.h>
  18#include <linux/file.h>
  19#include <linux/namei.h>
  20#include <linux/poll.h>
  21#include <linux/mount.h>
  22#include <linux/statfs.h>
  23#include <linux/ctype.h>
  24#include <linux/string.h>
  25#include <linux/fs_struct.h>
  26#include "internal.h"
  27
  28static int cachefiles_daemon_open(struct inode *, struct file *);
  29static int cachefiles_daemon_release(struct inode *, struct file *);
  30static ssize_t cachefiles_daemon_read(struct file *, char __user *, size_t,
  31                                      loff_t *);
  32static ssize_t cachefiles_daemon_write(struct file *, const char __user *,
  33                                       size_t, loff_t *);
  34static unsigned int cachefiles_daemon_poll(struct file *,
  35                                           struct poll_table_struct *);
  36static int cachefiles_daemon_frun(struct cachefiles_cache *, char *);
  37static int cachefiles_daemon_fcull(struct cachefiles_cache *, char *);
  38static int cachefiles_daemon_fstop(struct cachefiles_cache *, char *);
  39static int cachefiles_daemon_brun(struct cachefiles_cache *, char *);
  40static int cachefiles_daemon_bcull(struct cachefiles_cache *, char *);
  41static int cachefiles_daemon_bstop(struct cachefiles_cache *, char *);
  42static int cachefiles_daemon_cull(struct cachefiles_cache *, char *);
  43static int cachefiles_daemon_debug(struct cachefiles_cache *, char *);
  44static int cachefiles_daemon_dir(struct cachefiles_cache *, char *);
  45static int cachefiles_daemon_inuse(struct cachefiles_cache *, char *);
  46static int cachefiles_daemon_secctx(struct cachefiles_cache *, char *);
  47static int cachefiles_daemon_tag(struct cachefiles_cache *, char *);
  48
  49static unsigned long cachefiles_open;
  50
  51const struct file_operations cachefiles_daemon_fops = {
  52        .owner          = THIS_MODULE,
  53        .open           = cachefiles_daemon_open,
  54        .release        = cachefiles_daemon_release,
  55        .read           = cachefiles_daemon_read,
  56        .write          = cachefiles_daemon_write,
  57        .poll           = cachefiles_daemon_poll,
  58        .llseek         = noop_llseek,
  59};
  60
  61struct cachefiles_daemon_cmd {
  62        char name[8];
  63        int (*handler)(struct cachefiles_cache *cache, char *args);
  64};
  65
  66static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
  67        { "bind",       cachefiles_daemon_bind          },
  68        { "brun",       cachefiles_daemon_brun          },
  69        { "bcull",      cachefiles_daemon_bcull         },
  70        { "bstop",      cachefiles_daemon_bstop         },
  71        { "cull",       cachefiles_daemon_cull          },
  72        { "debug",      cachefiles_daemon_debug         },
  73        { "dir",        cachefiles_daemon_dir           },
  74        { "frun",       cachefiles_daemon_frun          },
  75        { "fcull",      cachefiles_daemon_fcull         },
  76        { "fstop",      cachefiles_daemon_fstop         },
  77        { "inuse",      cachefiles_daemon_inuse         },
  78        { "secctx",     cachefiles_daemon_secctx        },
  79        { "tag",        cachefiles_daemon_tag           },
  80        { "",           NULL                            }
  81};
  82
  83
  84/*
  85 * do various checks
  86 */
  87static int cachefiles_daemon_open(struct inode *inode, struct file *file)
  88{
  89        struct cachefiles_cache *cache;
  90
  91        _enter("");
  92
  93        /* only the superuser may do this */
  94        if (!capable(CAP_SYS_ADMIN))
  95                return -EPERM;
  96
  97        /* the cachefiles device may only be open once at a time */
  98        if (xchg(&cachefiles_open, 1) == 1)
  99                return -EBUSY;
 100
 101        /* allocate a cache record */
 102        cache = kzalloc(sizeof(struct cachefiles_cache), GFP_KERNEL);
 103        if (!cache) {
 104                cachefiles_open = 0;
 105                return -ENOMEM;
 106        }
 107
 108        mutex_init(&cache->daemon_mutex);
 109        cache->active_nodes = RB_ROOT;
 110        rwlock_init(&cache->active_lock);
 111        init_waitqueue_head(&cache->daemon_pollwq);
 112
 113        /* set default caching limits
 114         * - limit at 1% free space and/or free files
 115         * - cull below 5% free space and/or free files
 116         * - cease culling above 7% free space and/or free files
 117         */
 118        cache->frun_percent = 7;
 119        cache->fcull_percent = 5;
 120        cache->fstop_percent = 1;
 121        cache->brun_percent = 7;
 122        cache->bcull_percent = 5;
 123        cache->bstop_percent = 1;
 124
 125        file->private_data = cache;
 126        cache->cachefilesd = file;
 127        return 0;
 128}
 129
 130/*
 131 * release a cache
 132 */
 133static int cachefiles_daemon_release(struct inode *inode, struct file *file)
 134{
 135        struct cachefiles_cache *cache = file->private_data;
 136
 137        _enter("");
 138
 139        ASSERT(cache);
 140
 141        set_bit(CACHEFILES_DEAD, &cache->flags);
 142
 143        cachefiles_daemon_unbind(cache);
 144
 145        ASSERT(!cache->active_nodes.rb_node);
 146
 147        /* clean up the control file interface */
 148        cache->cachefilesd = NULL;
 149        file->private_data = NULL;
 150        cachefiles_open = 0;
 151
 152        kfree(cache);
 153
 154        _leave("");
 155        return 0;
 156}
 157
 158/*
 159 * read the cache state
 160 */
 161static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
 162                                      size_t buflen, loff_t *pos)
 163{
 164        struct cachefiles_cache *cache = file->private_data;
 165        char buffer[256];
 166        int n;
 167
 168        //_enter(",,%zu,", buflen);
 169
 170        if (!test_bit(CACHEFILES_READY, &cache->flags))
 171                return 0;
 172
 173        /* check how much space the cache has */
 174        cachefiles_has_space(cache, 0, 0);
 175
 176        /* summarise */
 177        clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
 178
 179        n = snprintf(buffer, sizeof(buffer),
 180                     "cull=%c"
 181                     " frun=%llx"
 182                     " fcull=%llx"
 183                     " fstop=%llx"
 184                     " brun=%llx"
 185                     " bcull=%llx"
 186                     " bstop=%llx",
 187                     test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
 188                     (unsigned long long) cache->frun,
 189                     (unsigned long long) cache->fcull,
 190                     (unsigned long long) cache->fstop,
 191                     (unsigned long long) cache->brun,
 192                     (unsigned long long) cache->bcull,
 193                     (unsigned long long) cache->bstop
 194                     );
 195
 196        if (n > buflen)
 197                return -EMSGSIZE;
 198
 199        if (copy_to_user(_buffer, buffer, n) != 0)
 200                return -EFAULT;
 201
 202        return n;
 203}
 204
 205/*
 206 * command the cache
 207 */
 208static ssize_t cachefiles_daemon_write(struct file *file,
 209                                       const char __user *_data,
 210                                       size_t datalen,
 211                                       loff_t *pos)
 212{
 213        const struct cachefiles_daemon_cmd *cmd;
 214        struct cachefiles_cache *cache = file->private_data;
 215        ssize_t ret;
 216        char *data, *args, *cp;
 217
 218        //_enter(",,%zu,", datalen);
 219
 220        ASSERT(cache);
 221
 222        if (test_bit(CACHEFILES_DEAD, &cache->flags))
 223                return -EIO;
 224
 225        if (datalen < 0 || datalen > PAGE_SIZE - 1)
 226                return -EOPNOTSUPP;
 227
 228        /* drag the command string into the kernel so we can parse it */
 229        data = kmalloc(datalen + 1, GFP_KERNEL);
 230        if (!data)
 231                return -ENOMEM;
 232
 233        ret = -EFAULT;
 234        if (copy_from_user(data, _data, datalen) != 0)
 235                goto error;
 236
 237        data[datalen] = '\0';
 238
 239        ret = -EINVAL;
 240        if (memchr(data, '\0', datalen))
 241                goto error;
 242
 243        /* strip any newline */
 244        cp = memchr(data, '\n', datalen);
 245        if (cp) {
 246                if (cp == data)
 247                        goto error;
 248
 249                *cp = '\0';
 250        }
 251
 252        /* parse the command */
 253        ret = -EOPNOTSUPP;
 254
 255        for (args = data; *args; args++)
 256                if (isspace(*args))
 257                        break;
 258        if (*args) {
 259                if (args == data)
 260                        goto error;
 261                *args = '\0';
 262                args = skip_spaces(++args);
 263        }
 264
 265        /* run the appropriate command handler */
 266        for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
 267                if (strcmp(cmd->name, data) == 0)
 268                        goto found_command;
 269
 270error:
 271        kfree(data);
 272        //_leave(" = %zd", ret);
 273        return ret;
 274
 275found_command:
 276        mutex_lock(&cache->daemon_mutex);
 277
 278        ret = -EIO;
 279        if (!test_bit(CACHEFILES_DEAD, &cache->flags))
 280                ret = cmd->handler(cache, args);
 281
 282        mutex_unlock(&cache->daemon_mutex);
 283
 284        if (ret == 0)
 285                ret = datalen;
 286        goto error;
 287}
 288
 289/*
 290 * poll for culling state
 291 * - use POLLOUT to indicate culling state
 292 */
 293static unsigned int cachefiles_daemon_poll(struct file *file,
 294                                           struct poll_table_struct *poll)
 295{
 296        struct cachefiles_cache *cache = file->private_data;
 297        unsigned int mask;
 298
 299        poll_wait(file, &cache->daemon_pollwq, poll);
 300        mask = 0;
 301
 302        if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
 303                mask |= POLLIN;
 304
 305        if (test_bit(CACHEFILES_CULLING, &cache->flags))
 306                mask |= POLLOUT;
 307
 308        return mask;
 309}
 310
 311/*
 312 * give a range error for cache space constraints
 313 * - can be tail-called
 314 */
 315static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
 316                                         char *args)
 317{
 318        kerror("Free space limits must be in range"
 319               " 0%%<=stop<cull<run<100%%");
 320
 321        return -EINVAL;
 322}
 323
 324/*
 325 * set the percentage of files at which to stop culling
 326 * - command: "frun <N>%"
 327 */
 328static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
 329{
 330        unsigned long frun;
 331
 332        _enter(",%s", args);
 333
 334        if (!*args)
 335                return -EINVAL;
 336
 337        frun = simple_strtoul(args, &args, 10);
 338        if (args[0] != '%' || args[1] != '\0')
 339                return -EINVAL;
 340
 341        if (frun <= cache->fcull_percent || frun >= 100)
 342                return cachefiles_daemon_range_error(cache, args);
 343
 344        cache->frun_percent = frun;
 345        return 0;
 346}
 347
 348/*
 349 * set the percentage of files at which to start culling
 350 * - command: "fcull <N>%"
 351 */
 352static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
 353{
 354        unsigned long fcull;
 355
 356        _enter(",%s", args);
 357
 358        if (!*args)
 359                return -EINVAL;
 360
 361        fcull = simple_strtoul(args, &args, 10);
 362        if (args[0] != '%' || args[1] != '\0')
 363                return -EINVAL;
 364
 365        if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
 366                return cachefiles_daemon_range_error(cache, args);
 367
 368        cache->fcull_percent = fcull;
 369        return 0;
 370}
 371
 372/*
 373 * set the percentage of files at which to stop allocating
 374 * - command: "fstop <N>%"
 375 */
 376static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
 377{
 378        unsigned long fstop;
 379
 380        _enter(",%s", args);
 381
 382        if (!*args)
 383                return -EINVAL;
 384
 385        fstop = simple_strtoul(args, &args, 10);
 386        if (args[0] != '%' || args[1] != '\0')
 387                return -EINVAL;
 388
 389        if (fstop < 0 || fstop >= cache->fcull_percent)
 390                return cachefiles_daemon_range_error(cache, args);
 391
 392        cache->fstop_percent = fstop;
 393        return 0;
 394}
 395
 396/*
 397 * set the percentage of blocks at which to stop culling
 398 * - command: "brun <N>%"
 399 */
 400static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
 401{
 402        unsigned long brun;
 403
 404        _enter(",%s", args);
 405
 406        if (!*args)
 407                return -EINVAL;
 408
 409        brun = simple_strtoul(args, &args, 10);
 410        if (args[0] != '%' || args[1] != '\0')
 411                return -EINVAL;
 412
 413        if (brun <= cache->bcull_percent || brun >= 100)
 414                return cachefiles_daemon_range_error(cache, args);
 415
 416        cache->brun_percent = brun;
 417        return 0;
 418}
 419
 420/*
 421 * set the percentage of blocks at which to start culling
 422 * - command: "bcull <N>%"
 423 */
 424static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
 425{
 426        unsigned long bcull;
 427
 428        _enter(",%s", args);
 429
 430        if (!*args)
 431                return -EINVAL;
 432
 433        bcull = simple_strtoul(args, &args, 10);
 434        if (args[0] != '%' || args[1] != '\0')
 435                return -EINVAL;
 436
 437        if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
 438                return cachefiles_daemon_range_error(cache, args);
 439
 440        cache->bcull_percent = bcull;
 441        return 0;
 442}
 443
 444/*
 445 * set the percentage of blocks at which to stop allocating
 446 * - command: "bstop <N>%"
 447 */
 448static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
 449{
 450        unsigned long bstop;
 451
 452        _enter(",%s", args);
 453
 454        if (!*args)
 455                return -EINVAL;
 456
 457        bstop = simple_strtoul(args, &args, 10);
 458        if (args[0] != '%' || args[1] != '\0')
 459                return -EINVAL;
 460
 461        if (bstop < 0 || bstop >= cache->bcull_percent)
 462                return cachefiles_daemon_range_error(cache, args);
 463
 464        cache->bstop_percent = bstop;
 465        return 0;
 466}
 467
 468/*
 469 * set the cache directory
 470 * - command: "dir <name>"
 471 */
 472static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
 473{
 474        char *dir;
 475
 476        _enter(",%s", args);
 477
 478        if (!*args) {
 479                kerror("Empty directory specified");
 480                return -EINVAL;
 481        }
 482
 483        if (cache->rootdirname) {
 484                kerror("Second cache directory specified");
 485                return -EEXIST;
 486        }
 487
 488        dir = kstrdup(args, GFP_KERNEL);
 489        if (!dir)
 490                return -ENOMEM;
 491
 492        cache->rootdirname = dir;
 493        return 0;
 494}
 495
 496/*
 497 * set the cache security context
 498 * - command: "secctx <ctx>"
 499 */
 500static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
 501{
 502        char *secctx;
 503
 504        _enter(",%s", args);
 505
 506        if (!*args) {
 507                kerror("Empty security context specified");
 508                return -EINVAL;
 509        }
 510
 511        if (cache->secctx) {
 512                kerror("Second security context specified");
 513                return -EINVAL;
 514        }
 515
 516        secctx = kstrdup(args, GFP_KERNEL);
 517        if (!secctx)
 518                return -ENOMEM;
 519
 520        cache->secctx = secctx;
 521        return 0;
 522}
 523
 524/*
 525 * set the cache tag
 526 * - command: "tag <name>"
 527 */
 528static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
 529{
 530        char *tag;
 531
 532        _enter(",%s", args);
 533
 534        if (!*args) {
 535                kerror("Empty tag specified");
 536                return -EINVAL;
 537        }
 538
 539        if (cache->tag)
 540                return -EEXIST;
 541
 542        tag = kstrdup(args, GFP_KERNEL);
 543        if (!tag)
 544                return -ENOMEM;
 545
 546        cache->tag = tag;
 547        return 0;
 548}
 549
 550/*
 551 * request a node in the cache be culled from the current working directory
 552 * - command: "cull <name>"
 553 */
 554static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
 555{
 556        struct path path;
 557        const struct cred *saved_cred;
 558        int ret;
 559
 560        _enter(",%s", args);
 561
 562        if (strchr(args, '/'))
 563                goto inval;
 564
 565        if (!test_bit(CACHEFILES_READY, &cache->flags)) {
 566                kerror("cull applied to unready cache");
 567                return -EIO;
 568        }
 569
 570        if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
 571                kerror("cull applied to dead cache");
 572                return -EIO;
 573        }
 574
 575        /* extract the directory dentry from the cwd */
 576        get_fs_pwd(current->fs, &path);
 577
 578        if (!S_ISDIR(path.dentry->d_inode->i_mode))
 579                goto notdir;
 580
 581        cachefiles_begin_secure(cache, &saved_cred);
 582        ret = cachefiles_cull(cache, path.dentry, args);
 583        cachefiles_end_secure(cache, saved_cred);
 584
 585        path_put(&path);
 586        _leave(" = %d", ret);
 587        return ret;
 588
 589notdir:
 590        path_put(&path);
 591        kerror("cull command requires dirfd to be a directory");
 592        return -ENOTDIR;
 593
 594inval:
 595        kerror("cull command requires dirfd and filename");
 596        return -EINVAL;
 597}
 598
 599/*
 600 * set debugging mode
 601 * - command: "debug <mask>"
 602 */
 603static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
 604{
 605        unsigned long mask;
 606
 607        _enter(",%s", args);
 608
 609        mask = simple_strtoul(args, &args, 0);
 610        if (args[0] != '\0')
 611                goto inval;
 612
 613        cachefiles_debug = mask;
 614        _leave(" = 0");
 615        return 0;
 616
 617inval:
 618        kerror("debug command requires mask");
 619        return -EINVAL;
 620}
 621
 622/*
 623 * find out whether an object in the current working directory is in use or not
 624 * - command: "inuse <name>"
 625 */
 626static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
 627{
 628        struct path path;
 629        const struct cred *saved_cred;
 630        int ret;
 631
 632        //_enter(",%s", args);
 633
 634        if (strchr(args, '/'))
 635                goto inval;
 636
 637        if (!test_bit(CACHEFILES_READY, &cache->flags)) {
 638                kerror("inuse applied to unready cache");
 639                return -EIO;
 640        }
 641
 642        if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
 643                kerror("inuse applied to dead cache");
 644                return -EIO;
 645        }
 646
 647        /* extract the directory dentry from the cwd */
 648        get_fs_pwd(current->fs, &path);
 649
 650        if (!S_ISDIR(path.dentry->d_inode->i_mode))
 651                goto notdir;
 652
 653        cachefiles_begin_secure(cache, &saved_cred);
 654        ret = cachefiles_check_in_use(cache, path.dentry, args);
 655        cachefiles_end_secure(cache, saved_cred);
 656
 657        path_put(&path);
 658        //_leave(" = %d", ret);
 659        return ret;
 660
 661notdir:
 662        path_put(&path);
 663        kerror("inuse command requires dirfd to be a directory");
 664        return -ENOTDIR;
 665
 666inval:
 667        kerror("inuse command requires dirfd and filename");
 668        return -EINVAL;
 669}
 670
 671/*
 672 * see if we have space for a number of pages and/or a number of files in the
 673 * cache
 674 */
 675int cachefiles_has_space(struct cachefiles_cache *cache,
 676                         unsigned fnr, unsigned bnr)
 677{
 678        struct kstatfs stats;
 679        struct path path = {
 680                .mnt    = cache->mnt,
 681                .dentry = cache->mnt->mnt_root,
 682        };
 683        int ret;
 684
 685        //_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
 686        //       (unsigned long long) cache->frun,
 687        //       (unsigned long long) cache->fcull,
 688        //       (unsigned long long) cache->fstop,
 689        //       (unsigned long long) cache->brun,
 690        //       (unsigned long long) cache->bcull,
 691        //       (unsigned long long) cache->bstop,
 692        //       fnr, bnr);
 693
 694        /* find out how many pages of blockdev are available */
 695        memset(&stats, 0, sizeof(stats));
 696
 697        ret = vfs_statfs(&path, &stats);
 698        if (ret < 0) {
 699                if (ret == -EIO)
 700                        cachefiles_io_error(cache, "statfs failed");
 701                _leave(" = %d", ret);
 702                return ret;
 703        }
 704
 705        stats.f_bavail >>= cache->bshift;
 706
 707        //_debug("avail %llu,%llu",
 708        //       (unsigned long long) stats.f_ffree,
 709        //       (unsigned long long) stats.f_bavail);
 710
 711        /* see if there is sufficient space */
 712        if (stats.f_ffree > fnr)
 713                stats.f_ffree -= fnr;
 714        else
 715                stats.f_ffree = 0;
 716
 717        if (stats.f_bavail > bnr)
 718                stats.f_bavail -= bnr;
 719        else
 720                stats.f_bavail = 0;
 721
 722        ret = -ENOBUFS;
 723        if (stats.f_ffree < cache->fstop ||
 724            stats.f_bavail < cache->bstop)
 725                goto begin_cull;
 726
 727        ret = 0;
 728        if (stats.f_ffree < cache->fcull ||
 729            stats.f_bavail < cache->bcull)
 730                goto begin_cull;
 731
 732        if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
 733            stats.f_ffree >= cache->frun &&
 734            stats.f_bavail >= cache->brun &&
 735            test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
 736            ) {
 737                _debug("cease culling");
 738                cachefiles_state_changed(cache);
 739        }
 740
 741        //_leave(" = 0");
 742        return 0;
 743
 744begin_cull:
 745        if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
 746                _debug("### CULL CACHE ###");
 747                cachefiles_state_changed(cache);
 748        }
 749
 750        _leave(" = %d", ret);
 751        return ret;
 752}
 753
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